Inhibitory properties of some heavy metals on carbonic anhydrase I and II isozymes activities purified from Van Lake fish (Chalcalburnus Tarichi) gill Müslüm Kuzu & Veysel Çomaklı & Ebru Akkemik & Mehmet Çiftci & Ömer İrfan Küfrevioğlu Received: 28 December 2017 /Accepted: 27 March 2018 # Springer Science+Business Media B.V., part of Springer Nature 2018 Abstract In this study, CA I and II isoenzymes were purified from Van Lake fish gills by using Sepharose- 4B-L-tyrosine-sulfanilamide affinity chromatography and to determine the effects of some metals on the enzyme activities. For purified CA I isoenzyme, yield, specific activity, and purification fold were obtained as 42.07%, 4948.12 EU/mg protein, and 116.61 and for CA II isoenzyme, 7%, 1798.56 EU/mg protein, and 42.38 respectively. Activity of CA was determined by measuring “CO 2 -hydratase activity”. Purity control was checked by SDS-PAGE. In vitro inhibitory effect of Cu 2+ , Ag + , Cd 2+ , Ni 2+ metal ions, and arsenic (V) oxide were also examined for both isozymes activities. Where- as Cu 2+ , Ag + , Cd 2+ , and Ni 2+ ions showed inhibitory effects on both isozymes, arsenic (V) oxide showed activation effect. IC 50 values were calculated by draw- ing activity %-[I] graphs for metal ions exhibiting in- hibitory effects. IC 50 values were determined as 3.39, 6.38, 13.52, and 206 μM for CA I isozyme and 6.16, 20.29, 46, and 223 μM for CA II isozyme respectively. Keywords Carbonic anhydrase . Heavy metal . Inhibition . Purification Introduction Lake Van fish (Chalcalburnus tarichi, Pearl mullet) is a member of the Cypriniformes family, which is an en- demic species living in the Lake Van. The Lake Van is one of the saltiest lakes known in the world. Due to these extreme conditions of the lake (salinity 22% and pH 9.8), only a vertebrate species and a few invertebrate species live in the lake. The only living vertebrate species in the lake is the endemic Lake Van fish (Kuzu et al. 2016). Carbonic anhydrase (EC 4.2.1.1 CA) is ubiquitous metalloenzyme family that catalyzes the reversible hydration/dehydration of carbon dioxide to HCO 3 - and H + , being involved in many physiological processes. CA isozymes participate in important biological processes such as acid-base regulation, respiration, carbon dioxide and ion transport, gluconeogenesis, lipogenesis, ureogenesis, electrolyte secretion, bone resorption, and tumorigenesis in different tissues by simplifying inter- conversion of carbon dioxide to HCO 3 - (Şentürk et al. 2011). Up to now, 16 different CA isoforms have been determined with their biochemical properties, subcellular Fish Physiol Biochem https://doi.org/10.1007/s10695-018-0499-8 M. Kuzu (*) Faculty of Pharmacy, University of Ağrıİbrahim Çeçen, 04100 Ağrı, Turkey e-mail: mkuzu@agri.edu.tr V. Çomaklı School of Healthy, University of Ağrıİbrahim Çeçen, 04100 Ağrı, Turkey E. Akkemik Faculty of Engineering and Architecture, Siirt University, 56100 Siirt, Turkey M. Çiftci Faculty of Science and Letters, Bingöl University, 12000 Bingöl, Turkey Ö. İ. Küfrevioğlu Faculty of Science, Atatürk University, 25240 Erzurum, Turkey